Tipless lamp stem



' Get, 7, 1924. T

, 1,5105% A. BRANN TIBLESS LAMP STEM Filed -June 2, 1921 ATTORNEY To allwhom it may concern:

ALBERT- BRAINN, a citizen of the United States, and a resident EBTBanner, or near cannon, NEW J Be it known that I,

of East Orange, in the county of Essex and State of New Jersey, haveinvented a new and useful Improvement in Tipless Lamp Stems, of whichthe following is a specification. I

This invention relates to the manufacture of stems for incandescentelectric lamps of the tipless type. An object of this invention is toprovide a stem composed of several parts or portions of glasses havingselected characteristics which permit the portions to be joined orsealed together in a satisfactory and stable manner.

Another and more particular object is to provide a novel stem for anincandescent lamp having an exhust tube, the inherent characteristic ofone of the parts of which.

difi'ers from a similar characteristic of each of the other parts of thestem, such difference being present to an extent that permits the partsto be joined by scaling in such manner as to avoid excessive strains.

In accordance with the well known practice of manufacturing tiplesslamps, an exhaust tube is consolidated with the stem.- However, inperforming this operation, excessive strains develop in the glass partsof the stem and such strains, subsequently produce cracks and breaks,thus rendering the. finished lamp useless. This invention, ashereinafter outlined, embodies a novel and satisfactory method ofovercoming these defects.

In the accom anying drawings: a I Fig. 1 is a si e view, partly insection, of the parts of a'steni of an incandescent lamp in assembledposition; and, j

2 is aside view of a completed stem, showing an exhaust tube in positionand an opening leading from the exterior of the stem to the interior ofthe exhaust tube.

I Referring to the drawings and particularly to Fig. 1, the individualparts or pertions of a stem of an. incandescent lamp are illustrated. asassembled in the usual or overla ped position ready; to be heated'andpresse to ether to form a stem. These parts usua y consist of a stem orflare tube 5 having a flared portion 6, an arbor 7- for supporting the.filament, leading-in con- Application filed June 2, 1921. Serial N0.474,487.

ductors 8 and an exhaust tube 9; all of these elements being positionedas illustrated in order that they may be consolidated in the seal formedby pressing the partstogether when in plastic condition.

3 Referring to Fig. 2 a completed stem is." shown, with the arbor, flaretube and ex-' haust tube joined to form a seal. This 1 I 1.; nssrenoa r0wns'rmenousn a: 1 comam', n coarona'rron or rnnnsrnvenra.

seal is usually known as the press and is represented in the drawing at10. An opening or. passageway 11 leadi from the 11 allows the air to beexhausted from the lamp bulb after the stem has been scaled therein. Thetipping ofi' after the exexhaust tube to the exterior of t e stem may Ibe formed directly after the press has been haustion of the air isusually performed at i a constriction 12 in the exhaust tube.

Heretofore, in the manufacture of stems of the eneral constructionillustrated in Fig. 2, It has been found, thatcracks and breaks developenear the seal and especial? at the juncture of the tubes 6 and 9. t hasalso been found that, without any apparent reason, some of these cracksandbreaks develope within a .few hours after the formation of the stemsand that some of these defects develope during the manufacturingofieration of sealing the stems into the bulb. y reason of thedevelopment of these defects, a special inspection of the and anotherafter the stem has been sealed to; the bulb, have been necessary. Thesestems before they are assembled in the bulb I inspections increase theultimate cost of the finished product and are to be avoided if possible.

In the prior construction of lamp stems,

the flare, and exhust tubes have been con- 1 structed of glasses havingsubstantiall the same linear coefficients of expansion; en

the exhaust tube is concentrically ositioned that, in forming the press,excessive strains are within the flare tube it is foun developed,probably due to the unequal cooling as cracks and breaks develops inmahng of the stem which strains subseguently. manifest themselves byaging or uring' subsequent operations.

' factory union of these parts is obtained when sealed together.- i,

In forming a seal in a stem between glasses having difierentcoeii'icients of exlv pension, it is to be noted that the end oi theexhaust tube is positioned concentric with the flare tube and expandsand contracts during the, heating operation, this expansion 0 andcontraction being dependent upon the coeficient of expansion of theglass comrising the exhaust tube. -'lhis exhaust tube, aving a smallercoefii'cient of expansion than the flare tube, does not expand andcontract to the same degree as the flare tube;

with the result that, when these parts hecome cooled after the formationof the press the exhaust tube apparently is not grippe or placed dersuch great compression byv the flare tube contracting around it and thusafibrds a means for relieving excessive strains in the glasses composingthe parts consolidated at the point ofthe press.

By employing glass parts having different characteristics, a stem may beconstructed which satisfactorily meets the requirements of manufacture.It is, however, to be understood that the degree of variation may bevaried by employing glasses of difi'erent thiclmiess and by giving fullconsideration to-the positions in which the glasses are held to formseals, as, for example, when one of the parts is to be heldconcentrically to an-. other of the parts, it must be considered thatthere will be a pressing of the outer glass upon the inner glass. Asatisfactory stem for tipless lamps is obtained by employing stems durina dare tube made of glass having a cosmcient of expansion approximating.92 x 10 and an exhaust tube made of glass having a. coeficient ofexpansion varying between .83 x10 and .85 x 10.

lln forming the seals in the stems of an incandescent lamp by the abovedescribed method and by' employing glasses which have difierentcharacteristics, it is found that the stems may be subjected to a muchharder and careless handling than heretofore and that the operators, inhandling the the operation of sealing the stems into t e bulbs, are notrequired to exercise great caution. The ability to form the newcombination of glasses in order to readily handle and form the sealbetween the completed stem and the lamp bulb without the cracking orbreaking ofl of the exintone-o haust tube, materially increases thechiciency of the manufacture of incandescent electric lamps andsubstantially reduces the cost of manufacture.

lit is to be understood that various modifications may be made in thestems constructed and in the method of torrnin the stems, and suchmodifications are to be included within the see e of thisinvention outlined in the totlowing claims.

What is claimed is:

i. A stem for an incandescent lamp the tipless t comprising aplttralifn' glass parts, t e several parts oi ferent coeficients ofexpansion and cs posed when sealed, that the inner portion of the sealwill be of a lesser cocient of expansion than the surfaos of the seal.

2. A lamp stem comprising leading-in wires, a ll tube and an exhausttube, said tubes being consolidated in a about the leadingdn wires, said.ss having a lower coefficient of expamiion within than on the surfaw.

3. A stem for an incandescent lamp of the tipless type comprising.aflare tube and an exhaust tube sealed thereto, said .ust tube having alinear coeficient of expon lower than that of the flare tube.

t. A stem for an incandescent lamp oi? the tipless type having anexhaust tube consituting a part of the stem, said exhaust tube having'acoeficient of expansion considerably lower than the coefiicient of nsionof another part of said 5. la a stem construction of an incandt lamp,the combination of a dare tube, an exhaust tube sealed in a positionwithin said flare tube, the coeihcient or expension of said exhaust tubeapproximating .84 x 10 and the coeficient of expansion or the flare tubeapproximating .92 x 10.

6. In a stem for a tiplcss incandescent lamp, the combination of a lesstube having one of its ends flared, said glass having a linearcoefiicient of expansion approximatin .92 x 10 a glass arbor forsupporting a amp filament, leading-m conductors, a glass exhaust tubehaving a consmiction between its ends, said last named gl havtill ' inga linear coeficient of expansion varyin between .83 x 10 and .85 x 10,said tubes, arbor and conductors being sealed to-v gether to form aunit.

7. The method of preventing cracks in lamp of the tipless type which comprises providing the component parts of the stem of difiereutcoeficients or expansion, disposing a part having the lower coeilicientof expansion within another part, heating to render the parts plasticand pitting the parts to cool and unite without settin up detrimentalstrains by virtue of the dullerenoe in their coeficients of expansion.

8. The method of pneventing cracks in lamp stems of the tipless typewhich oomprises providing a flare tube of a given 00- efficient ofexpansion and an exhaust tube of a smaller ooefiicient of expansion,disposing a portion of the exhaust tube within the flare tube, applyingheat to render the overlapping portions plastic, permitting the portionsto cool and unite without subseguent cracks by virtue of the differencein egree of their coefficients of expansion.

In testimony whereof, I have hereunto subscrib 1921.

ed my name this 1st day of June ALBERT BRANN.

